Electrical characterization of CaCu3Ti4O12 (CCTO) ceramics with scanning probe based techniques has been carried out. In particular, conductive atomic force microscopy (C-AFM) and scanning impedance microscopy (SIM) have been used to demonstrate the presence, shape and size in CCTO ceramics of the different electrically domains, both at the grain boundaries and within the grains. The electrical characteristics of single grains and of single domains have been evaluated and it has been observed that the conductive grains are surrounded by insulating grain boundaries.